The paper aims to identify the failure of the components and elements and the evaluation of their consequence on the functioning of the functional subsystems (installations, equipments) from an HPP.On the basis of the values of randomize variable lifetime (LT) and maintenance correcting time (TMC), defined in the previous paper, they were determined the indicators of operational reliability at the level of hydro- generator group and there subsystems.With the view of identification and hierarchy the impact of component elements on the reliability of the groups, it was done in the paper an analysis of the failures causes for each subsystems of group not only under the aspects of faults interval but also of the number faults. The obtained results being represented under graphical form.